As shown in FIG. 5, a hydraulic shovel 1 is a work machine provided with a lower structure, an upper swing body 3, a cab 4, and a work device 5. The lower structure has right and left traveling devices 2 adapted to be respectively driven by right and left travel motors 2m. The upper swing body 3 is adapted to be rotated on the lower structure by a swing motor 3m. The cab 4 and the work device 5 are mounted on the upper swing body 3. The work device 5 comprises a boom 6 adapted to be vertically pivoted by boom cylinders 6c, a stick 7 to be pivoted by a stick cylinder 7c, and a bucket 8 to be pivoted by a bucket cylinder 8c, wherein the base end of the boom 6 is supported at the upper swing body 3 by a shaft; the stick 7 is supported at the distal end of the boom 6 by a shaft; and the bucket 8 is supported at the distal end of the stick 7 by a shaft.
In the cab 4 of a typical hydraulic shovel structured as above, traveling pedals and travel levers for operating the right and left traveling devices 2 of the lower structure are disposed on the floor in front of the operating seat.
Operating the traveling pedals with the feet is sufficient for broad travel operation but inadequate to perform fine operation. Therefore, when performing fine operation with a travel lever, it is necessary for the operator to remove a hand from one of the operating levers (work device/swing operating levers) that are disposed at the right and left sides of the operating seat respectively to rotate the upper swing body 3 or the work device 5, and reach for the travel lever, which is disposed in front of the operator.
Furthermore, when separately operating the right and left travel levers, it is necessary to reach forward with both hands.
Therefore, a structure that includes travel levers disposed in front of the operating seat may cause the travel levers to obstruct the operator from entering or exiting the cab 4, or it compels the operator to change his position or shift his hand when operating a travel lever.
Some examples of conventionally known structures to solve the above problems include providing a travel control lever in the proximity of a work device/swing operating lever disposed at a side of the operating seat (e. g. See Japanese Laid-open Patent Publication No. 6-136778; (page 4 and FIG. 9); Japanese Laid-open Patent Publication No. 7-32901 (page 3 and FIG. 2); Japanese Laid-open Patent Publication No. 2002-323931 (page 4 and FIG. 1) and Japanese Laid-open Patent Publication No. 2004-100397 (pages 7 and 15-17, and FIGS. 1 and 11)).
These structures facilitate entering and exiting of the operator but do not solve the problem of switching the hand from the operating lever to perform traveling operation. Moreover, sufficient space for installation of the travel lever has to be allotted at a side of the operating seat.
Other structures are known, in which a switchover device is provided to enable one of the two work device/swing operating levers to serve as a travel lever (e. g. See Japanese Laid-open Patent Publication No. 7-119710 (pages 2-3 and FIG. 1) and Japanese Laid-open Patent Publication No. 2000-27238 (pages 4-7 and FIG. 1)).
Furthermore, yet other structures are known, in which the right and left work device/swing operating levers are enabled to respectively and independently operate the right and left traveling devices (e. g. See Japanese Laid-open Patent Publication No. 2004-100397 (pages 7 and 15-17, and FIGS. 1 and 11)) and Patent Document 7: Japanese Laid-open Patent Publication No. H09-165788 (pages 3-4 and FIGS. 3-4).
In any one of the structures that are offered in the Patent Documents mentioned above and include a switchover device provided separately from the operating levers, the operator has to remove his hand from an operating lever in order to operate the switchover device, which is nearly as inconvenient as switching one's hand from one lever to another. Even if the switchover device is attached to an operating lever, it is difficult for the operator to ascertain whether switchover has taken place, and the operator has to think about which device the operating lever has engaged for operation at the moment.